// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

(() => {
    // Map multiple JavaScript environments to a single common API,
    // preferring web standards over Node.js API.
    //
    // Environments considered:
    // - Browsers
    // - Node.js
    // - Electron
    // - Parcel

    if (typeof global !== "undefined") {
        // global already exists
    } else if (typeof window !== "undefined") {
        window.global = window;
    } else if (typeof self !== "undefined") {
        self.global = self;
    } else {
        throw new Error("cannot export Go (neither global, window nor self is defined)");
    }

    if (!global.require && typeof require !== "undefined") {
        global.require = require;
    }

    if (!global.fs && global.require) {
        global.fs = require("fs");
    }

    const enosys = () => {
        const err = new Error("not implemented");
        err.code = "ENOSYS";
        return err;
    };

    if (!global.fs) {
        let outputBuf = "";
        global.fs = {
            constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1 }, // unused
            writeSync(fd, buf) {
                outputBuf += decoder.decode(buf);
                const nl = outputBuf.lastIndexOf("\n");
                if (nl != -1) {
                    console.log(outputBuf.substr(0, nl));
                    outputBuf = outputBuf.substr(nl + 1);
                }
                return buf.length;
            },
            write(fd, buf, offset, length, position, callback) {
                if (offset !== 0 || length !== buf.length || position !== null) {
                    callback(enosys());
                    return;
                }
                const n = this.writeSync(fd, buf);
                callback(null, n);
            },
            chmod(path, mode, callback) { callback(enosys()); },
            chown(path, uid, gid, callback) { callback(enosys()); },
            close(fd, callback) { callback(enosys()); },
            fchmod(fd, mode, callback) { callback(enosys()); },
            fchown(fd, uid, gid, callback) { callback(enosys()); },
            fstat(fd, callback) { callback(enosys()); },
            fsync(fd, callback) { callback(null); },
            ftruncate(fd, length, callback) { callback(enosys()); },
            lchown(path, uid, gid, callback) { callback(enosys()); },
            link(path, link, callback) { callback(enosys()); },
            lstat(path, callback) { callback(enosys()); },
            mkdir(path, perm, callback) { callback(enosys()); },
            open(path, flags, mode, callback) { callback(enosys()); },
            read(fd, buffer, offset, length, position, callback) { callback(enosys()); },
            readdir(path, callback) { callback(enosys()); },
            readlink(path, callback) { callback(enosys()); },
            rename(from, to, callback) { callback(enosys()); },
            rmdir(path, callback) { callback(enosys()); },
            stat(path, callback) { callback(enosys()); },
            symlink(path, link, callback) { callback(enosys()); },
            truncate(path, length, callback) { callback(enosys()); },
            unlink(path, callback) { callback(enosys()); },
            utimes(path, atime, mtime, callback) { callback(enosys()); },
        };
    }

    if (!global.process) {
        global.process = {
            getuid() { return -1; },
            getgid() { return -1; },
            geteuid() { return -1; },
            getegid() { return -1; },
            getgroups() { throw enosys(); },
            pid: -1,
            ppid: -1,
            umask() { throw enosys(); },
            cwd() { throw enosys(); },
            chdir() { throw enosys(); },
        }
    }

    if (!global.crypto) {
        const nodeCrypto = require("crypto");
        global.crypto = {
            getRandomValues(b) {
                nodeCrypto.randomFillSync(b);
            },
        };
    }

    if (!global.performance) {
        global.performance = {
            now() {
                const [sec, nsec] = process.hrtime();
                return sec * 1000 + nsec / 1000000;
            },
        };
    }

    if (!global.TextEncoder) {
        global.TextEncoder = require("util").TextEncoder;
    }

    if (!global.TextDecoder) {
        global.TextDecoder = require("util").TextDecoder;
    }

    // End of polyfills for common API.

    const encoder = new TextEncoder("utf-8");
    const decoder = new TextDecoder("utf-8");

    global.Go = class {
        constructor() {
            this.argv = ["js"];
            this.env = {};
            this.exit = (code) => {
                if (code !== 0) {
                    console.warn("exit code:", code);
                }
            };
            this._exitPromise = new Promise((resolve) => {
                this._resolveExitPromise = resolve;
            });
            this._pendingEvent = null;
            this._scheduledTimeouts = new Map();
            this._nextCallbackTimeoutID = 1;

            const setInt64 = (addr, v) => {
                this.mem.setUint32(addr + 0, v, true);
                this.mem.setUint32(addr + 4, Math.floor(v / 4294967296), true);
            }

            const getInt64 = (addr) => {
                const low = this.mem.getUint32(addr + 0, true);
                const high = this.mem.getInt32(addr + 4, true);
                return low + high * 4294967296;
            }

            const loadValue = (addr) => {
                const f = this.mem.getFloat64(addr, true);
                if (f === 0) {
                    return undefined;
                }
                if (!isNaN(f)) {
                    return f;
                }

                const id = this.mem.getUint32(addr, true);
                return this._values[id];
            }

            const storeValue = (addr, v) => {
                const nanHead = 0x7FF80000;

                if (typeof v === "number") {
                    if (isNaN(v)) {
                        this.mem.setUint32(addr + 4, nanHead, true);
                        this.mem.setUint32(addr, 0, true);
                        return;
                    }
                    if (v === 0) {
                        this.mem.setUint32(addr + 4, nanHead, true);
                        this.mem.setUint32(addr, 1, true);
                        return;
                    }
                    this.mem.setFloat64(addr, v, true);
                    return;
                }

                switch (v) {
                    case undefined:
                        this.mem.setFloat64(addr, 0, true);
                        return;
                    case null:
                        this.mem.setUint32(addr + 4, nanHead, true);
                        this.mem.setUint32(addr, 2, true);
                        return;
                    case true:
                        this.mem.setUint32(addr + 4, nanHead, true);
                        this.mem.setUint32(addr, 3, true);
                        return;
                    case false:
                        this.mem.setUint32(addr + 4, nanHead, true);
                        this.mem.setUint32(addr, 4, true);
                        return;
                }

                let id = this._ids.get(v);
                if (id === undefined) {
                    id = this._idPool.pop();
                    if (id === undefined) {
                        id = this._values.length;
                    }
                    this._values[id] = v;
                    this._goRefCounts[id] = 0;
                    this._ids.set(v, id);
                }
                this._goRefCounts[id]++;
                let typeFlag = 1;
                switch (typeof v) {
                    case "string":
                        typeFlag = 2;
                        break;
                    case "symbol":
                        typeFlag = 3;
                        break;
                    case "function":
                        typeFlag = 4;
                        break;
                }
                this.mem.setUint32(addr + 4, nanHead | typeFlag, true);
                this.mem.setUint32(addr, id, true);
            }

            const loadSlice = (addr) => {
                const array = getInt64(addr + 0);
                const len = getInt64(addr + 8);
                return new Uint8Array(this._inst.exports.mem.buffer, array, len);
            }

            const loadSliceOfValues = (addr) => {
                const array = getInt64(addr + 0);
                const len = getInt64(addr + 8);
                const a = new Array(len);
                for (let i = 0; i < len; i++) {
                    a[i] = loadValue(array + i * 8);
                }
                return a;
            }

            const loadString = (addr) => {
                const saddr = getInt64(addr + 0);
                const len = getInt64(addr + 8);
                return decoder.decode(new DataView(this._inst.exports.mem.buffer, saddr, len));
            }

            const timeOrigin = Date.now() - performance.now();
            this.importObject = {
                go: {
                    // Go's SP does not change as long as no Go code is running. Some operations (e.g. calls, getters and setters)
                    // may synchronously trigger a Go event handler. This makes Go code get executed in the middle of the imported
                    // function. A goroutine can switch to a new stack if the current stack is too small (see morestack function).
                    // This changes the SP, thus we have to update the SP used by the imported function.

                    // func wasmExit(code int32)
                    "runtime.wasmExit": (sp) => {
                        const code = this.mem.getInt32(sp + 8, true);
                        this.exited = true;
                        delete this._inst;
                        delete this._values;
                        delete this._goRefCounts;
                        delete this._ids;
                        delete this._idPool;
                        this.exit(code);
                    },

                    // func wasmWrite(fd uintptr, p unsafe.Pointer, n int32)
                    "runtime.wasmWrite": (sp) => {
                        const fd = getInt64(sp + 8);
                        const p = getInt64(sp + 16);
                        const n = this.mem.getInt32(sp + 24, true);
                        fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n));
                    },

                    // func resetMemoryDataView()
                    "runtime.resetMemoryDataView": (sp) => {
                        this.mem = new DataView(this._inst.exports.mem.buffer);
                    },

                    // func nanotime1() int64
                    "runtime.nanotime1": (sp) => {
                        setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000);
                    },

                    // func walltime1() (sec int64, nsec int32)
                    "runtime.walltime1": (sp) => {
                        const msec = (new Date).getTime();
                        setInt64(sp + 8, msec / 1000);
                        this.mem.setInt32(sp + 16, (msec % 1000) * 1000000, true);
                    },

                    // func scheduleTimeoutEvent(delay int64) int32
                    "runtime.scheduleTimeoutEvent": (sp) => {
                        const id = this._nextCallbackTimeoutID;
                        this._nextCallbackTimeoutID++;
                        this._scheduledTimeouts.set(id, setTimeout(
                            () => {
                                this._resume();
                                while (this._scheduledTimeouts.has(id)) {
                                    // for some reason Go failed to register the timeout event, log and try again
                                    // (temporary workaround for https://github.com/golang/go/issues/28975)
                                    console.warn("scheduleTimeoutEvent: missed timeout event");
                                    this._resume();
                                }
                            },
                            getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
                        ));
                        this.mem.setInt32(sp + 16, id, true);
                    },

                    // func clearTimeoutEvent(id int32)
                    "runtime.clearTimeoutEvent": (sp) => {
                        const id = this.mem.getInt32(sp + 8, true);
                        clearTimeout(this._scheduledTimeouts.get(id));
                        this._scheduledTimeouts.delete(id);
                    },

                    // func getRandomData(r []byte)
                    "runtime.getRandomData": (sp) => {
                        crypto.getRandomValues(loadSlice(sp + 8));
                    },

                    // func finalizeRef(v ref)
                    "syscall/js.finalizeRef": (sp) => {
                        const id = this.mem.getUint32(sp + 8, true);
                        this._goRefCounts[id]--;
                        if (this._goRefCounts[id] === 0) {
                            const v = this._values[id];
                            this._values[id] = null;
                            this._ids.delete(v);
                            this._idPool.push(id);
                        }
                    },

                    // func stringVal(value string) ref
                    "syscall/js.stringVal": (sp) => {
                        storeValue(sp + 24, loadString(sp + 8));
                    },

                    // func valueGet(v ref, p string) ref
                    "syscall/js.valueGet": (sp) => {
                        const result = Reflect.get(loadValue(sp + 8), loadString(sp + 16));
                        sp = this._inst.exports.getsp(); // see comment above
                        storeValue(sp + 32, result);
                    },

                    // func valueSet(v ref, p string, x ref)
                    "syscall/js.valueSet": (sp) => {
                        Reflect.set(loadValue(sp + 8), loadString(sp + 16), loadValue(sp + 32));
                    },

                    // func valueDelete(v ref, p string)
                    "syscall/js.valueDelete": (sp) => {
                        Reflect.deleteProperty(loadValue(sp + 8), loadString(sp + 16));
                    },

                    // func valueIndex(v ref, i int) ref
                    "syscall/js.valueIndex": (sp) => {
                        storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)));
                    },

                    // valueSetIndex(v ref, i int, x ref)
                    "syscall/js.valueSetIndex": (sp) => {
                        Reflect.set(loadValue(sp + 8), getInt64(sp + 16), loadValue(sp + 24));
                    },

                    // func valueCall(v ref, m string, args []ref) (ref, bool)
                    "syscall/js.valueCall": (sp) => {
                        try {
                            const v = loadValue(sp + 8);
                            const m = Reflect.get(v, loadString(sp + 16));
                            const args = loadSliceOfValues(sp + 32);
                            const result = Reflect.apply(m, v, args);
                            sp = this._inst.exports.getsp(); // see comment above
                            storeValue(sp + 56, result);
                            this.mem.setUint8(sp + 64, 1);
                        } catch (err) {
                            storeValue(sp + 56, err);
                            this.mem.setUint8(sp + 64, 0);
                        }
                    },

                    // func valueInvoke(v ref, args []ref) (ref, bool)
                    "syscall/js.valueInvoke": (sp) => {
                        try {
                            const v = loadValue(sp + 8);
                            const args = loadSliceOfValues(sp + 16);
                            const result = Reflect.apply(v, undefined, args);
                            sp = this._inst.exports.getsp(); // see comment above
                            storeValue(sp + 40, result);
                            this.mem.setUint8(sp + 48, 1);
                        } catch (err) {
                            storeValue(sp + 40, err);
                            this.mem.setUint8(sp + 48, 0);
                        }
                    },

                    // func valueNew(v ref, args []ref) (ref, bool)
                    "syscall/js.valueNew": (sp) => {
                        try {
                            const v = loadValue(sp + 8);
                            const args = loadSliceOfValues(sp + 16);
                            const result = Reflect.construct(v, args);
                            sp = this._inst.exports.getsp(); // see comment above
                            storeValue(sp + 40, result);
                            this.mem.setUint8(sp + 48, 1);
                        } catch (err) {
                            storeValue(sp + 40, err);
                            this.mem.setUint8(sp + 48, 0);
                        }
                    },

                    // func valueLength(v ref) int
                    "syscall/js.valueLength": (sp) => {
                        setInt64(sp + 16, parseInt(loadValue(sp + 8).length));
                    },

                    // valuePrepareString(v ref) (ref, int)
                    "syscall/js.valuePrepareString": (sp) => {
                        const str = encoder.encode(String(loadValue(sp + 8)));
                        storeValue(sp + 16, str);
                        setInt64(sp + 24, str.length);
                    },

                    // valueLoadString(v ref, b []byte)
                    "syscall/js.valueLoadString": (sp) => {
                        const str = loadValue(sp + 8);
                        loadSlice(sp + 16).set(str);
                    },

                    // func valueInstanceOf(v ref, t ref) bool
                    "syscall/js.valueInstanceOf": (sp) => {
                        this.mem.setUint8(sp + 24, loadValue(sp + 8) instanceof loadValue(sp + 16));
                    },

                    // func copyBytesToGo(dst []byte, src ref) (int, bool)
                    "syscall/js.copyBytesToGo": (sp) => {
                        const dst = loadSlice(sp + 8);
                        const src = loadValue(sp + 32);
                        if (!(src instanceof Uint8Array)) {
                            this.mem.setUint8(sp + 48, 0);
                            return;
                        }
                        const toCopy = src.subarray(0, dst.length);
                        dst.set(toCopy);
                        setInt64(sp + 40, toCopy.length);
                        this.mem.setUint8(sp + 48, 1);
                    },

                    // func copyBytesToJS(dst ref, src []byte) (int, bool)
                    "syscall/js.copyBytesToJS": (sp) => {
                        const dst = loadValue(sp + 8);
                        const src = loadSlice(sp + 16);
                        if (!(dst instanceof Uint8Array)) {
                            this.mem.setUint8(sp + 48, 0);
                            return;
                        }
                        const toCopy = src.subarray(0, dst.length);
                        dst.set(toCopy);
                        setInt64(sp + 40, toCopy.length);
                        this.mem.setUint8(sp + 48, 1);
                    },

                    "debug": (value) => {
                        console.log(value);
                    },
                }
            };
        }

        async run(instance) {
            this._inst = instance;
            this.mem = new DataView(this._inst.exports.mem.buffer);
            this._values = [ // JS values that Go currently has references to, indexed by reference id
                NaN,
                0,
                null,
                true,
                false,
                global,
                this,
            ];
            this._goRefCounts = []; // number of references that Go has to a JS value, indexed by reference id
            this._ids = new Map();  // mapping from JS values to reference ids
            this._idPool = [];      // unused ids that have been garbage collected
            this.exited = false;    // whether the Go program has exited

            // Pass command line arguments and environment variables to WebAssembly by writing them to the linear memory.
            let offset = 4096;

            const strPtr = (str) => {
                const ptr = offset;
                const bytes = encoder.encode(str + "\0");
                new Uint8Array(this.mem.buffer, offset, bytes.length).set(bytes);
                offset += bytes.length;
                if (offset % 8 !== 0) {
                    offset += 8 - (offset % 8);
                }
                return ptr;
            };

            const argc = this.argv.length;

            const argvPtrs = [];
            this.argv.forEach((arg) => {
                argvPtrs.push(strPtr(arg));
            });
            argvPtrs.push(0);

            const keys = Object.keys(this.env).sort();
            keys.forEach((key) => {
                argvPtrs.push(strPtr(`${key}=${this.env[key]}`));
            });
            argvPtrs.push(0);

            const argv = offset;
            argvPtrs.forEach((ptr) => {
                this.mem.setUint32(offset, ptr, true);
                this.mem.setUint32(offset + 4, 0, true);
                offset += 8;
            });

            this._inst.exports.run(argc, argv);
            if (this.exited) {
                this._resolveExitPromise();
            }
            await this._exitPromise;
        }

        _resume() {
            if (this.exited) {
                throw new Error("Go program has already exited");
            }
            this._inst.exports.resume();
            if (this.exited) {
                this._resolveExitPromise();
            }
        }

        _makeFuncWrapper(id) {
            const go = this;
            return function () {
                const event = { id: id, this: this, args: arguments };
                go._pendingEvent = event;
                go._resume();
                return event.result;
            };
        }
    }

    if (
        global.require &&
        global.require.main === module &&
        global.process &&
        global.process.versions &&
        !global.process.versions.electron
    ) {
        if (process.argv.length < 3) {
            console.error("usage: go_js_wasm_exec [wasm binary] [arguments]");
            process.exit(1);
        }

        const go = new Go();
        go.argv = process.argv.slice(2);
        go.env = Object.assign({ TMPDIR: require("os").tmpdir() }, process.env);
        go.exit = process.exit;
        WebAssembly.instantiate(fs.readFileSync(process.argv[2]), go.importObject).then((result) => {
            process.on("exit", (code) => { // Node.js exits if no event handler is pending
                if (code === 0 && !go.exited) {
                    // deadlock, make Go print error and stack traces
                    go._pendingEvent = { id: 0 };
                    go._resume();
                }
            });
            return go.run(result.instance);
        }).catch((err) => {
            console.error(err);
            process.exit(1);
        });
    }
})();